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Oracle Enqueue Deadlocks Per Txn

Oracle Consulting Tips by Burleson


The Enqueue Deadlocks Per Txn Oracle metric is the number of times per transaction that a process detected a potential deadlock when exchanging two buffers and raised an internal, restartable error.

Steve Adams notes on enqueue deadlocks:

"ORA-4020 - deadlock detected while trying to lock object 29 October 1999
An application is trying to insert into a table and gets an ORA-4020 error.

Looking at the V$LOCK view shows a TS lock being held. I restarted the database and the TS lock had disappeared. We reran the application and about a minute later this lock had reappeared. Any idea where else I could look to find out more about this problem?

This error message relates to library cache lock deadlocks, not enqueue lock deadlocks. V$LOCK is only appropriate for enqueue locking issues. To investigate library cache locking issues, you need to use DBA_KGLLOCK which is created by the $ORACLE_HOME/rdbms/admin/catblock.sql script."

This, and many other Oracle performance metrics are discussed in my book "Oracle Tuning" by Rampant TechPress.  You can buy it directly from the publisher and save 30% at this link:



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